Identification of random loads impinging on the RAH-66 Comanche Helicopter empennage using spectral analysis
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Authors
Mason, Patrick H.
Subjects
RAH-66 Comanche Helicopter
Random Vibrations
Comanche Tail Section
Structural Analysis
Spectral Analysis
NASTRAN Analysis
Random Vibrations
Comanche Tail Section
Structural Analysis
Spectral Analysis
NASTRAN Analysis
Advisors
Wood, E. Roberts
Danielson, Donald A.
Gordis, Joshua H.
Date of Issue
1998-06
Date
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
The Army RAH-66 ComancheHelicopter is currently undergoing developmental flight testing. Theempennage of the aircraft isexperiencing buffeting where the horizontal and vertical tail vibrate at resonant frequencies. These high buffet loads are manifested in higher than anticipated fitting loads, particularly on the tail, and vibrations in the crew stations and at the nose cone where the targeting sensors are located. Significant effort has been devoted to identifying the sources of excitation and the nature of the structural response. This thesis determines the location andmagnitude of empennage vibratory airloads. Because the nature of the excitation is a random function, spectral analysis is used. To obtain the loads, a three step process was utilized. First, from aircraft differential pressure transducers and accelerometers, the spectral content of theresponse and excitation was determined. Then, using aNASTRAN model modified to replicate the flight test aircraft, frequency response functions were determined between selected points on the aircraft's tail and the accelerometers. Finally, using this information, a solution was obtained for the vibratory airloads. Having provided information on the nature of the driving forces, structural modifications can be made that move the natural frequencies away from thefrequencies of the applied airloads
Type
Thesis
Description
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NPS Report Number
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Format
viii, 146 p.;28 cm.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.